Television transmitting system



March 21, 0 H SCHA TELEVISION TRANSMITTING SYSTEM Filed Jan. 51, 1942 6ESE WEE-3 M AT-T?W Patented Mar. 21, 1944 TELEVISION TRANSMITTING SYSTEMOtto H. Schade, West Caldwell, N. J assignor to Radio Corporation ofAmerica, a corporation of Delaware Application January 31, 1942, SerialNo. 429,008

Claims.

This invention relates to television transmit ting systems and moreparticularly to improvements in systems used in connection with storagetype television transmitting tubes in which the storage or mosaicelectrode is inclined with respect to the axis of the scanning beamelectron gun structure.

A television transmitting system must necessarily include some elementor device for transferring or converting an optical image into a seriesof electrical picture signals. One apparatus for effecting such aconversion is the iconoscope which includes an electron gun structurefor generating a focused cathode ray beam and a mosaic electrode uponwhich a charge image is produced in response to the projection of anoptical light image on the mosaic. The mosaic electrode is then scannedin bilateral directions in order to remove the charge image and in orderto produce electrical potential variations representative of the opticalimage projected thereon.

In the receiver a television picture reproducing tube is normallyemployed and such a tube may, for example, be the kinescope. Thekinescope or picture reproducing tube also includes an electron gunstructure for producing a focused cathode ray beam and additional meansare provided for causing the cathode ray beam to be directed against andto scan a target area or fluorescent surface. As the cathode ray beam inthe receiving tube is deflected in synchronism with correspondingdeflections of the scanning beam in the television transmitting tube,the current intensity of the cathode ray beam in the receiving tube ismodulated in order to produce varying efiects on the fluorescent targetelectrode to reproduce the television image. The modulations of thecathode ray beam in the receiving tube are naturally controlled inaccordance with the received picture signals transmitted from thetransmitting station. In the receiving tube the target electrode isnormally positioned at right angles to the axis of the electron gunstructure and the axis of symmetry of the electron gun structure isnormally directed at a point near the center of the target electrode. Inthe transmitting tube and particularly in tubes of the iconoscope type,the mosaic electrode is positioned at an angle with respect to theelectron gun structure in order that an optical image may be projectedon the surface of the mosa c electrode and in order that the samesurface of the mosaic electrode may be scanned by the cathode ray beamgenerated in the tube.

The commonly termed pin-cushion distortion results in the area scannednot being perfectly square or rectangular. This lack of rectangularityin so far as the scanned area is concerned may be compensated for in thedesign of the deflecting electrodes or the deflecting yoke.

In the transmitting tube, however, in view of the fact that the targetelectrode is inclined at an angle with respect to the axis of theelectron gun structure, the electrical distortion or lack ofrectangularity of the scanned area is not symmetrical or'uniform at allof the edges of the area with the result that complete correction may beaccomplished by non-symmetrical design of the deflecting electrodes orthe electromagnetic deflecting yoke. Variations in the dimensions of thetube, however, naturally require alterations in the corrections of thedeflecting yoke. Most of the distortion or lack of rectangularity in thearea scanned by the electron beam in the televi sion transmitting tubeis in. the horizontal deflection direction of the cathode ray beam andparticularly at that portion of the mosaic electrode most removed fromthe electron gun structure. Furthermore, after a television transmittingtube has been constructed and by reason of the various processes thatthe tube must undergo in the steps of manufacturing the tube, the mosaicelectrode may in some instances become warped and by reason of thisslight possible warping, a slight additional distortion is produced. g

It is therefore one purpose of the present invention to provide a systemwherein the scanning cathode ray beam in a television transmitting tubeof the iconoscope type may be caused to traverse or scan a perfectlyrectangular area.

Another purpose of the present invention resides in the provision ofcircuit means at the television transmitting tube for causing thescanning cathode ray beam to traverse the mosaic electrode in straighthorizontal lines irrespective of the particular portion of the mosaicelectrode being traversed.

Still another purpose of the present invention resides in the provisionof means in a television transmitter wherein compensating or auxiliarydeflecting potentials may be superimposed or combined with the principalor fundamental deflecting voltages in order to compensate for any lackof rectangularity in the area scanned by the cathode ray beam.

Another purpose of the present invention resides in the provision ofmeans whereby the cathode ray beammay be subjected to a slightadditional vertical deflection component when the beam is near themiddle portion of a scanned line in addition to the deflecting force orfleld to which the beam is subjected when the beam is near either end ofthe scanned lines.

A still further purpose of the present invention resides in theprovision of a relatively simple and effective circuit arrangementwhereby the cathode ray beam in a television transmitting tube of theiconoscope type may be caused to scan a substantially rectangular areaon the mosaic electrode regardless of slight warped conditions of themosaic electrode and the circuit also includes means whereby the degreeor intensity of the compensating deflection voltages may bev controlledto render the system applicable to any particular tube even thoughslight differences and variations may exist between various televisiontransmitting tubes.

Still other purposes and advantages of the present invent on will becomemore apparent to those skilled in the art from the following detaileddescription of the invention particularly when considered in connectionwith the drawing wherein:

Figure 1 shows one preferred form of the present invention.

Figure 2 shows in relatively simple detail the construction of atelevision transmitting tube of the iconoscope type.

Figure 3 represents the area that would be scanned on the surface of themosaic electrode if no compensatin voltages were incorporated in thedeflectin circuit.

Figure 4 shows the area that would be scanned on the surface of themosaic electrode after electrical keystone correction and pin-cush ondistortion correctionsffor the vertical side curvature) have beenintroduced but without the correct ons accomplished by the presentinvention.

Figure 5 shows a curve representing one form of voltage variation thatmay be used to accomplish the purposes of this invent on and p Figure 6shows a curve representing the voltage variations appearing at one partof the circuit shown in Figure 1.

Referring now to the drawing there is shown in Figure 2 a televisiontransmitt ng tube of the iconoscope type. The tube includes an envelope2 of glass or ceramic material and inside the tube is positioned amosaic or target electrode 4. The tube also includes an electron gunstructure generally represented at 6 for producing a focused cathode raybeam and for deflecting the focused beam in substantially mutuallyperpend cular directions a deflecting yoke 8 is provided. A lens systemH) is also shown associated with the television transmitting tube bymeans of which an optical image of an object I2 may be focused upon thesurface of the mosaic electrode 4. It will be observed in Figure 2 thatthe mosaic elec -trode 4 is not positioned normal to the axis of theelectron gun structure 6 but is instead positioned at an angle withrespect thereto in order not to obstruct light rays which are focusedupon the mosaic electrode to produce the optical image. Inasmuch as thecathode ray beam scans the same side of the mosaic electrode upon whichthe optical image is projected, the gun structure must necessarily bepositioned at an angle with respect to the mosaic electrode.

In Figure l is shown partially schematically and partially in detail thecircuit arrangement necessary for effecting thedesired deflection of thecathode ray beam in a television transmit television field repetit onrate. frequency voltage variations are then applied to a verticaldeflection generator 22 which is deting tube. The system includes amaster oscillator it which preferably operates at line deflection ordouble line deflection frequency. The frequency of operation of themaster oscillator therefore depends upon the number of line elements ineach television frame together with the number of television framestraversed or transmitted per second. The master oscillator then suppliesvoltage variations of line or horizontal deflection frequency to ahorizontal deflection generator ill. The horizontal deflection generator produces voltage variations of the desired wave form to deflect thecathode ray beam at a uniform rate in a horizontal direction. The masteroscillator also supplies voltage variations or impulses to a frequencydivider 20 which may include counter circuits or frequency dividercircuits .for reducing the frequency of the voltage variations. Theoutput from the frequency divider 20, therefore, corresponds to thenumber of vertical deflections of the cathode ray beam or, in otherwords, the frequency corresponds to the These reduced signed to producethe required voltage variations for deflecting the cathode ray beam in avertical direction. Details of .the horizontal and vertical deflectiongenerators i8 and 22 will not be con sidered at this time since anysuitable horizontal and vertical deflection generators may be used. Suchgenerators are quite well known to those skilled in the art.

The output from the horizontal deflection generator is applied to ahorizontal deflection output tube 24. The tube includes a cathode 26, acontrol electrode 28 and an anode 30. The control electrode 28 isconnected to ground by the usual grid or control electrode resistor 32and the output from the horizontal deflection generator I8 is applied tothe control electrode 28 by way of coupling condenser 34. The cathode 26of the horizontal deflection output tube is connected to ground by wayof a: potentiometer 36 and the resistance element of the potentiometeris bypassed by a condenser 38. For maintaining the anode 30 positivewith respect to the cathode 26. the anode is connected to a positiveterminal 40 by way of the primary of the output transformer $2. Thesecondary of transformer 42 supplies energy to the horizontal deflectingcoils 44, these coils being included in the deflecting yoke 8 shown inFigure 2. The usual horizontal damping tube 46 is shown connected acrossthe secondary of transformer 42 in order to absorb the transientfollowing the high inductive voltage peak produced during the instant ofbeam return. Furthermore, a potentiometer 48 is also included in thecircuit, one endof the resistance element of the potentiometer beingconnected to ground while the other end of the resistance element of thepotentiometer is connected to a source of negative potential. By meansof this potentiometer an adjustable direct current component may becaused to flow through the horizontal deflecting coils 44 in order tocontrol the horizontal position of the scanned pattern on the mosaicelectrode 4 of the television transmitting tube 2. This method ofcentering the scanned pattern is well known to those skilled in the art.

The output from the vertical deflection gener ator 22 is appliedsimilarly to a vertical deflection output tube 50. This tube includes acathode 52, a control electrode 54 and an anode 56. The

control electrode is connected to ground by way of the usual gridresistor 58 while the voltage variations derived from the verticaldeflection generator 22 are applied to the control electrode 54 by theway of coupling condenser 60. The cathode 52 is connected to ground byvariable resistance 62, the resistance being by-passed to ground by anappropriate condenser 64. For maintaining the anode 56 positive withrespect to its cathode 52, the anode is connected, byway of the primaryof transformer 68, to terminal 66 to which a positive potential isapplied. When voltage variations are applied to the control electrode 54of the vertical deflection output tube and these voltage variations areamplified they in turn appear at the secondary of transformer 68 and arethen applied to the vertical deflecting coils 10. The verticaldeflecting coils are also incorporated in the deflecting yoke 8 shown inFigure 2. For centering the scanned area in a vertical direction, apotentiometer I2 is provided, the purpose of the potentiometer being topermit the circulation of a small direct current in the one direction oranother through the vertical deflecting coils in a manner well known inthe art.

Furthermore, by providing means whereb the cathode resistance 62 may beadjusted the linearity Of the vertical deflection may also becontrolled.

With the system as so far described, the cathode ray beam in atelevision transmitting tube may be caused to be deflected insubstantially mutually perpendicular directions across the surface ofthe mosaic electrode 4. For indicating the area traversed, reference isnow made to Fig ure 3 wherein the dotted rectangle A--BC--D representsthe desired area to be scanned. Actually'the area ABE--F will be scannedby the cathode ray beam when the deflecting coils 44 and 10, which arecontained in the deflecting yoke 8, are subjected to the voltagevariations produced by the system as above described. The arrows shownin Figure 3 represent the direction of scanning and although thesedirections are exactly opposite to the directions that the picture isreproduced in the receiver, it must be remembered that the optical imageon the mosaic electrode is inverted and reversed from left to right. Theuseful horizontal deflections of the cathode ray beam over the mosaicelectrode are thereforefrom left to right while the useful verticaldeflections are from the bottom of the mosaic to the top. It will benoticed that the area A--BE-F that is actually scanned is considerablydi torted (the distortions are in fact exaggerated in Figure 3 in orderto more clearly describe the invention and in order that it may be moreclearly understood) and these distortions may be referred to broadly askeystone distortion and pin-cushion distortion. The fact that the topedge of the mosaic is more removed from the electron gun structure thanis the bottom edge, a keystone shape pattern or area is traversed. InFigure 3 the horizontal curved line A--B at the top of the picture isconsiderably longer than the horizontal curvedline E-F at the bottom ofthe picture. Furthermore, all four of the boundary edges of the scannedarea are curved inwardly and this lack of linearity is generallyreferred to as pin-cushion distortion.

The keystone distortion may be simply and readily compensated for byvarying the degree of horizontal deflection in accordance with thevertical position of the cathode ray beam. One simple method foraccomplishing this is to modulate the amplitude of the horizontaldeflection voltages at vertical deflection frequency. Accordingly, inFigure 1, the vertical deflection generator 22 is shown as supplyingenergy, by way of conductor 2|, to the horizontal deflection generator1| 8. ,By this action it is possible to amplitude modulate thehorizontal deflection voltage variations at vertical deflectionfrequency. Since the matter of keystone correction is not the principalpurpose of the present invention and since circuits for compensating forkeystone distortion'are, well known in the art, a further discussion ofthe elimination of the inherent keystone distortion is believedunnecessary.

The so called pin-cushion distortion can be considerably reduced orsubstantially entirely eliminated by designing the electromagnetic,deflection yoke to compensate for this distortion. In fact, if thedegree of pin-cushion distortion is uniform at all 'four sides of thescanned area, it is possible .to completely eliminate the pin- -cushiondistortion. By reason of the fact, how ever, that the mosaic electrodeispositioned at an angle with respect to the axis of the electron gunstructure the pin-cushion distortion is not uniform and, as shown inFigure 3, is considerably reater at the top of the mosaic than itis nearthe bottom. It may be. seen in Figure 3 that the curvature of thescanned line A.B or the top edge of the scanned area is considerablygreater than the curvature of the scanned line along the bottom edge13-]? of the scanned area.

When keystone correction circuits are included in the deflectiongenerating network and when the deflection yoke has been so designed asto completely remove or compensate for all of the pin-cushiondistortion, the cathode ray beam will then traverse an area on themosaic electrode corresponding to the area bounded by the solid linesbetween the points G, H, J and K in Figure 4. It will be noticed inFigure 4 that'tbe scanned area is still not perfectly rectangular butextends below the desired boundary between the points G and H and alsoextends be low the desired boundary (or outside the boundary) betweenthe points J and K. The desiredhorizontal boundaries are represented bythe dotted lines in Figure 4. g

'The pin-cushion effect may be eliminated by proper design of thedeflection yoke for a tube of given fixed dimensions. Also, it ispossible, by proper keystone modulation, to cause the side boundariesbetween the points G-J'and H-K to' lie substantially along the desiredboundaries. Under these conditions and with careful design of the yoke,the cathode ray beam may be caused to scan a perfectly rectangularsurface provided, however, that the mosaic electrode is flat and alsoprovided that exact uniformity in the production of the televisiontransmitting tubes may be maintained. Since the production of televisiontransmitting tubes is rather involved and many steps must be included inthe process of making the tubes, exact electrical response uniformityand perfectly flat mosaic electrodes are difficult to assure.

Accordingly, in this invention, means have been provided in the beamdeflecting circuits for compensating for thepin-cushion and barreldistortion shown in Figure 4 which remains after a certain amount ofpin-cushion distortion has been compensated by design of the deflectingyoke and/or by modulated keystone correction circuits. It may be seen byinspecting Figure 4 that during the horizontal deflection of the cathoderay beam the vertical deflection component should be altered so that thepath traversed by the cathode ray beam in a horizontal direction will bein a straight line. It is therefore necessary that the cathode ray beambe subjected to a slightly greater deflection voltage when the beam isnear the middle of each scanned line than when it is near either end ofeach scanned line. The distortion between points G and H at the top ofthe mosaic exceeds the distortion between pointsJ and K at the bottom ofthe mosaic, but the deflecting force need not be gradually increased asthe beam is deflected in a vertical direction because the sameadditional deflecting force would cause a greater beam deflection at thetop of the mosaic because of the greater beam length. The intensity ofthe vertical deflecting field to which the cathode ray beam is subjectedmay therefore vary in a manner such as represented by the curve N inFigure 5. If the beam is subjected to a deflection frequency such asrepresented by the dotted line in Figure 5, then the beam will bedeflected in a vertical direction in a perfectly uniform manner and thecombination pin-cushion and barrel distortion shown in Figure 4 wouldnot be compensated for. In Figure 5 is shown a curve representing thevariation in the vertical deflecting field which should be imposed uponthe cathode ray beam to compensate for the distortion shown in Figure 4.For the sake of clarity, the curve shown at N in Figure 5 would apply toa sixline element picture, however it is to be understood that a verymuch larger number of lines would in fact be used. a

The horizontal deflection voltage variations are modulated at verticaldeflection frequency to compensate for keystone correction, andaccordingly the current flowing in the cathode resistance 36 of tube 24varies at horizontal or line deflection frequency and is modulated to asmall extent at vertical deflection frequency. Figure 6 shows at curve Ma wave form representing the potential variations at the cathode 25 ofthe horizontal deflection output tube 24. These potential variations maybe controlled somewhat as to Wave form by proper choice of the size ofthe condenser 38. This small variation in amplitude, as stated above, isa result of the effects of the keystone correction circuits incorporatedin the horizontal deflection generator l8.

The voltage variations of the wave form shown at M in Figure 6 aretherefore present at point M in the circuit shown in Figure 1 whichcorresponds to the movable contact of the potentiometer 38. The movablecontact of the potentiometer is then connected to one end of thesecondary winding of transformer 68 byway of series resistance 14 andcondenser 16'. 'The application of this voltage variation to thesecondary of transformer 68 therefore superimposes upon the verticaldeflection voltage variations a component of horizontal frequency havinga parabolic shape. There therefore results in the circuit including thesecondary of transformer 68 and the vertical deflecting coil a currentor voltage variation similar to the curve N in Figure 5. When such adeflecting potential is applied to the vertical deflecting coils thecathode ray beam may then be caused to scan a substantially perfectlyrectangular area on the surface of the mosaic electrode.

In order to control the intensity of the superimposed voltage variationsof parabolic shape and of line frequency, the potentiometer 3B isdesirable since by moving the position of the movable contact along thepotentiometer the intensity of the superimposed voltage variations maybe controlled in order that varying degrees of the combined pin-cushionand barrel distortions shown in Figure 4 may be compensated. Due topossible slight Warping of the mosaic electrode through processing andde-gassing of the television transmitting tube, it is desirable toinclude the adjustable feature since th amount of warping, if

any, will not be uniform in all tubes.

From the foregoing it may be seen, therefore, that a perfectlyrectangular area may be scanned on a mosaic electrode in an iconoscopetelevision transmitting tube even though the mosaic electrode isinclined at an angl with respect to the axis of symmetry of the electrongun structure and even though a slight amount of warping may in fact bepresent over the surface of the'mosaic electrode. Furthermore, it ispossible to vary the intensity of the compensating voltages in order topermit the required amount of compensation to be affected where thetelevision transmitting tubes are not exactly uniform.

Although the present; invention is described as applicable to a standardand conventional iconoscope, it is entirely possible for the inventionto be used with tubes of different design. Should the transmitting tubebe so constructed as to have the mosaic electrode positioned at an angleto the optical axis and normal with respect to the electron gunstructure, the invention could still be used to correct for combinationpin-cushion barrel distortion. 7 Furthermore, the invention is alsoapplicable to television transmitting tubes wherein the mosaic electrodeis of the double-faced type. that is where the optical image isprojected on one side of the mosaic and the scanning cathode ray beam isdirected against the other side of the mosaic, the mosaic beingpositioned normal to both the optical axis and the axis of symmetry ofthe electron gun structure.

Various. alterations and modifications of the present invention maybecome apparent to those skilled in the art and it is desirable that anyand all such modifications and alterations be considered within thepurview of th present invention except as limited by the hereinafterappanded claims.

I claim:

1. A television transmitter including a tran mitting tube having amosaic electrode and a cathode ray gun structure adapted to generate afocused beam of'electrons, means to produce an electrostatic chargeimage on said mosaic electrode, means to scan said mosaic electrode inhorizontal and vertical directions at predetermined different rates inorder to produce picture signals. said horizontal scanning meansincluding a discharge tube having a cathode, a control electrode and ananode, means including a resistance for connecting the cathode to apoint of fixed potential, means including a load circuit for maintainingthe anode positive with respect to the cathode, means for applyingvoltage variations of horizontal scanning frequency to the controlelectrode of said tube, said vertical scanning means including a seconddischarge tube having a cathode, a control electrode and an anode, meansincluding a load circuit for maintaining the anode positive with respectto the cathode, means to apply voltage variations of vertical scanningfrequency to the control electrode of said last mentioned tube, andmeans to apply a predetermined percentage of the potential variationspresent at the cathode of, said first mentioned tube to the anode loadcircuit of said second mentioned tube in order to compensate forinaccuracies in the pattern scanned by the cathode ray beam.

2. A television transmitter including a transmitting tube having amosaic electrode and a cathode ray gun structure adapted to generate afocused beam of electrons, means to produce an electrostatic chargeimage on said mosaic electrode, means to scan said mosaic electrode inhorizontal and vertical directions by the generated cathode ray beam atpredetermined different rates in order to produce picture signals, saidhorizontal scanning means including a first electron discharge tubehaving a cathode, a control electrode and an anode, means including aresistance for connecting the cathode to a point of fixed potential,means including a load circuit for maintaining the anode positive withrespect to the cathode, means for applying voltage variations ofhorizontal scanning frequency to the control electrode of said tube,said vertical scanning means including a second electron discharge tubehaving a cathode, a control electrode and an anode, means including aload circuit for maintaining the anode positive with respect to thecathode, means to apply voltage variations of vertical scanningfrequency to the control electrodev of said last mentioned tube, andmean to apply a predetermined intensity of the potential variations ofparabolic ,wave form and of horizontal scanning frequency to the anodeload circuit of said second mentioned tube in order to compensate forinaccuracies in the pattern scanned by the cathode ray beam.

3. A television transmitter including a transmitting tube having a lightresponsive mosaic electrode and a cathode ray gun structure adapted togenerate a focused beam of electrons, means for projecting an opticalimage on the mosaic electrode to produce an electrostatic charge imagethereon, means to scan said mosaic electrode in horizontal and verticaldirections at predetermined different rates by the generated cathode raybeam in order to produce picture signals, said horizontal scanning meansincluding a first electron discharge tube having a cathode, a controlelectrode and an anode, means including a resistance for connecting thecathode to a point of fixed potential, means including a load circuitfor maintaining the anode positive with respect to the cathode, meansfor applying voltage variations of horizontal scanning frequency to thecontrol electrode of said tube, said vertical scanning means including asecond electron discharge tube having a'cathode, a control electrode andan anode, means including a load circuit for maintaining the anodepositive with respect to the cathode, means to apply voltage variationsof vertical scanning frequency to the control electrode of said lastmentioned tube, and means to to apply a predetermined percentage of thepotential variations of parabolic wave form present at the cathode ofsaid first electron discharge tube to the anode load circuit of saidsecond electron discharge tube in order to compensate for inaccuraciesin the linearity of deflection of the cathode ray beam in the horizontaldirection.

4. A television transmitting system wherein a television transmittingtube is included for converting an optical image into a series oftelevision picture signals, said tube comprising a mosaic of horizontalbeam deflection frequency to the electrode and means adapted to generatea focused cathode ray beam, beam deflecting means for causing thegenerated cathode ray beam to be deflected across the mosaic at apredetermined rate in a horizontal direction, beam deflecting means forcausing the generated cathode ray beam to be deflected across the mosaicat a different predetermined rate in a vertical direction, saidhorizontal beam deflecting means including a first electron dischargetube having a cathode, a control electrode and an anode, means including a resistance for connecting the cathode of said tube to a point offixed potential, means including a load circuit for maintaining theanode of said tube positive with respect to its associated cathode,means for applying voltage variations control electrode of said tube,said vertical beam deflecting means including a second electrondischarge tube having a cathode, a control electrode and an anode, meansincluding a load circuit for maintaining the anode of said second tubepositive with respect to its associated cathode, means for applyingvoltage variations of vertical beam deflecting frequency to the controlelectrode of said second tube, and means including a series connectedresistance and condenser for super-. imposing a predetermined percentageof the voltage variations present at the cathode of said first dischargetube upon the voltage variations present at the anode loadcircuit ofsaid second discharge tube, whereby said cathode ray beam may be causedto scan a rectangular pattern on said mosaic electrode.

5. A television transmitting system wherein a television transmittingtube is'included for converting an optical image into a series ofpicture signals, said tube comprising a mosaic electrode and meansadapted to generate a'focused cathode ray beam, beam deflecting meansfor causing'the generated cathode ray beam to be deflected across themosaic at a predetermined rate in a horizontal direction, beamdeflecting means for causing the generated cathode ray beam tobedeflected across the mosaic at a different predetermined rate in avertical direction, said horizontal beam deflecting means including afirst electron discharge tube having a cathode, a control electrode andan anode, means including a resistance for connecting the cathode ofsaid tube to a point of flxed potential, a condenser connected inparallel with said resistance, means including a load circuit formaintaining the anode of said tube positive with respect to itsassociated cathode, means for applying voltage variations of horizontalbeam deflection frequency to the control electrode of said tube,'saidvertical beam deflecting means including a second electron dischargetube having a cathode, a control electrode and an anode, means includinga load circuit for maintaining the anode of said second tube positivewith respect to its associated cathode, means for applying voltagevariations of vertical beamdeflecting frequency to the control electrodeof said second tube, and means including a series connected impedanceand electron storage device for superimposing a predetermined percentageof the voltage variations of parabolic wave form present at the cathodeof said first discharge tube upon the voltage variations present in theload circuit of said second discharge tube, to thereby compensate forundesired variations in the pattern scanned by said cathode ray beam onsaid mosaic electrode.

6. A television transmitting system wherein a television transmittingtube is included for converting an optical image into a series ofpicture signals, said tube comprising a target electrode and meansadapted to generate a focused cathode ray beam, horizontal beamdeflecting means for causing the generated cathode ray beam to bedeflected horizontally across the mosaic at a predetermined rate,vertical beam deflecting means for causing the generated cathode raybeam to be deflected vertically across the mosaic at a differentpredetermined rate, said horizontal beam deflecting means including afirst electron discharge tube haw'ng a cathode, a control electrode andan anode, means including a resistance for connecting the cathode ofsaid tube to a point of fixed potential, a condenser connected inparallel with said resistance, means including a load circuit formaintaining the anode of said tube positive with respect to itsassociated cathode, means for applying voltage variations of horizontalbeam deflection frequency to the control electrode of said tube, saidvertical beam deflecting means including a second electron dischargetube having a cathode, a control electrode and an anode, means includinga load circuit for maintaining the anode of said second tube positivewith respect to its associated cathode, means for applying voltagevariations of vertical beam deflecting frequency to the controlelectrode of said second tube, and means for amplitude modulating thevoltage variations present at the anode of said second discharge tube bythe voltage variations of parabolic wave form present at the cathode ofsaid first discharge tube, whereby said cathode ray beam may be causedto be deflected linearly across said mosaic electrode in a horizontaldirection.

7. A system for use in a television transmitter for compensating forpin-cushion and barrel distortion comprising a television transmittingtube having a target electrode and means to produce a focused cathoderay beam, a first electron discharge tube having a cathode, a controlelectrode and an anode, means including a resistance for connecting thecathode to a point of fixed potential, means including a load circuitfor maintaining the anode positive with respect to its associatedcathode, means to apply voltage variations of one predetermined beamdefiection frequency to the control electrode of said discharge tube toproduce corresponding voltage variations in the load circuit of saidtube, means to utilize the voltage variations of said load circuit tocause the cathode ray beam to be deflected across the target electrodein one predetermined direction, a second electron discharge tube havinga cathode, a control electrode and an anode, means including a loadcircuit for maintaining the anode of said second discharge tube positivewith respect to its cathode, means to apply voltage variations ofanother predetermined beam deflection frequency to' the controlelectrode of said second discharge tube to produce corresponding voltagevariations in the load circuit of said tube, means to utilize thevoltage variations of said load circuit to cause the oathode ray beam tobe deflected across the target electrode in another predetermineddirection to thereby cause the cathodev ray beam to scan a predeterminedpattern on said target electrode, and means including a series connectedcondenser and resistance for superimposing a predetermined percentage ofthe voltage variations of parabolic wave form present at the cathode ofsaid first electron discharge tube upon the voltage variations presentin the load circuit of said second electron discharge tube, whereby thedeflection of the produced cathode ray beam at said anotherpredetermined beam deflection frequency will be in part controlled bythe voltage Variationsof said first predetermined frequency.

8. A system for use in a television transmitter for compensating forpin-cushion and barrel distortion comprising a television transmittingtube having a target electrode and means to produce a focused cathoderay beam, a first electron discharge tube having a cathode, a controlelectrode and an anode, means including a resistance for connecting thecathode to a point of fixed potential, a condenser connected in parallelwith said resistance, means including a load circuit for maintaining theanode positive with respect to its associated cathode, means to applyvoltage variations of horizontal beam. deflection frequency to thecontrol electrode of said discharge tube to produce correspondingvoltage variations in the load circuit of said tube, means to utilizethe voltage variations of said load circuit to cause the cathode raybeam'to be deflected across the target electrode in a horizontaldirection, a second electron discharge tube having a cathode, a controlelectrode and an anode, means including a load circuit for maintainingthe anode of said second discharge tube positive with respect to itscathode, means to apply voltage variations of vertical beam deflectionfrequency to the control electrode of'said second discharge tube toproduce corresponding voltage variations in the load circuit of saidtube, means to utilize the voltage variations of said load circuit tocause the cathode ray beam to be deflected across the target electrodein a vertical direction, and means for superimposing a predeterminedpercentage of the voltage variations of parabolic wave form present atthe cathode of said first electron discharge tube upon the voltagevariations present in the load circuit of said second electron dischargetube, whereby the deflection of the produced cathode ray beam in thehorizontal direction will be in part controlled by the voltagevariations of said first predetermined frequency to cause the cathoderay beam to be deflected linearly horizontally.

9. A system for use in a television system for compensating forpin-cushion and barrel distortion comprising a cathode ray tube having atarget electrode and means to produce a focused cathode ray beam,a'first electron discharge tube having a cathode, a control electrodeand an anode, means including a resistance for connecting the cathode toa point of fixed potential,

means including a load circuit for maintaining the anode positive withrespect to its associated cathode, means to apply voltage variations ofone predetermined beam deflection frequency to the control electrode ofsaid discharge tube to produce corresponding voltage variations in theload circuit of said tube, meansto utilize the voltage variations ofsaid load circuit to cause the cathode ray beam to be deflected acrossthe target electrode in one predetermined direction, a. second electrondischarge tube having a cathode, a control electrode and an anode, meansincluding a load circuit for maintaining the anode of said seconddischarge tube positive with respect to its cathode, means to applyvoltage variations oi another predetermined beam deflection frequency tothe control electrode of said second discharge tube to producecorresponding voltage variations in the load circuit of said tube, meansto utilize the voltage variations of said load circuit to cause thecathode ray beam to be deflected across the target electrode in anotherpredetermined direction, and means including a time constant circuit formixing a predetermined percentage of the voltage variations ofsubstantially parabolic wave form present at the cathode of said firstelectron discharge tube upon the voltage variations present in the loadcircuit of said second electron discharge tube, whereby the deflectionof the produced cathode ray beam in said another predetermined directionwill be partially controlled by the voltage variations of said firstpredetermined frequency to assure linearity of deflection of theproduced cathode ray beam in the last mentioned direction.

10. In a television apparatus wherein a cathode ray beam is controllablydeflected and caused to scan a mosaic electrode upon which a light imageis projected, including cathoderay beam deflecting means, a pair ofelectron discharge tubes each having a cathode, a control electrode andan anode, a resistance element for indicause the cathode ray beam toscan a bidimensional pattern on the mosaic electrode, and means tosuperimpose a predetermined percentage of the voltage variations ofparabolic wave form present at the cathode of one of the electrondischarge tubes upon the voltage variations present at the anode loadcircuit of the other electron discharge tubes to compensate forinaccuracies in the pattern scanned by the cathode ray beam.

OTTO H. SCHADE.

